Recent regulations have mandated the removal of ions such as chromate ion from waste streams to a maximum acceptable level. One of the ways to capture these removable ions is to use ion exchange resins in a fixed or fluidized bed. The advantage that a fluidized bed offers is that of greater rates of flowthrough and resistance to clogging by particulate impurities, but small particles are carried out of the fluidized bed thereby contaminating the effluent and losing expensive sorbent. These disadvantages can be overcome through permanent magnetization of the sorbent particles bu resident magnetism in these particles causes flocculation to occur anywhere in the apparatus and its associated plumbing.
In U.S. Pat. No. 4,115,927 Rosensweig discusses the prior art in which magnetic fields had been applied to fluidized beds of particles and then discloses a process for fluidizing magnetizable particles characterized by operating in a magnetic field at a superficial fluid velocity which avoids fluidization by bubbling at high velocities. While the term "fluid" is used, it is clear that Rosensweig's experiments were carried out with gases rather than liquids since only gases provide the bubbling action in the fluidized bed which the patentee wished to avoid. Further, the superficial velocities reported are typical of gases rather than liquids. As will be seen in the description of the present invention which follows, the inventors have found that carrying out a process in a bed of particles fluidized with liquid presents unique conditions not found in the Rosensweig patent.